After the basic triads and the 7th chords come ‘9th' chords. They are still diatonic, i.e. naturally occurring as a result of the Major scale, and are simply an upward extension of the same concepts that enabled us to arrive at the 7th chords.

To create 9th chords all we do is harmonize the scale as we have done before. We simply ‘stack' the intervals a little higher than we do for the seventh chords. The intervals C-E-G-B give us a C Major 7th chord. If we now stack another ‘third' interval, we will be adding a ‘D', and as a result we get a C Major9 chord.

When dealing with chords, we refer to the 2nd degree of the scale as a 9th. The ‘Add 9' chord is, for some reason, written by quite a lot of publishers of music and song books as ‘Cadd2', or they may even put C(2). This is one of those areas in which, unfortunately, there is not a lot of uniformity. However, major, minor and dominant 9th chords will not have that problem. They won't be written as ‘C ma 2', etc., but as CMA9, or C9, etc.

Let's look at the results of harmonizing the Major scale up to this point:

Degree

Triad

7th Chord

9th Chord

I

C

CMA7

CMA9

II

DMI

DMI7

DMI9

III

EMI

EMI7

— *

IV

F

FMA7

FMA9

V

G

G7

G9

VI

AMI

AMI7

AMI9

VII

B°

BMI7b5

— *

You can see that with the addition of ninth chords, the quality of the chords is unchanged. This means that degree V is still dominant, degree IV is still major, etc. However one very important thing to notice is that both degree III and degree VII don't have 9th chords at all.

This is because in a major scale there is only a semitone interval between degrees III and IV, and also between degrees VII and VIII. On degree III (in the example key of C, an E) we would need an F# to obtain a 9th interval from the degree III root. Of course we don't have one, as the scale goes from E to F.

On degree VII we would need a C# above the degree VII root, ‘B', and we don't have one of those in the C Major scale either. So Major scale degrees 3 or 7 cannot support a diatonic ninth chord. Once again this holds true for each Major key, not only our example of C major. Of course there is such a chord as ‘E Minor 9'. It's just not found in the key of C. Not so with degree VII however, as there is no ‘Minor 9 flat 5' chord.

These things are important to remember if you are a musician who improvises and likes to fill out chords a bit more in a song. For example: If you're playing a song in C Major, adding colourful chord tones to the basic arrangement, beware that an EMI9 chord will not work! Why? Because degrees III and VII of any Major key do not support a 9th chord. It is possible to play something groovy on a III chord, but not a 9th chord!

Here's a visual of what's been said, using the spellings of just the triads, 7ths and 9ths.

CHORD example

SPELLING

Major triad C

1, 3, 5 [ C, E, G ]

Major 7th CMA7

1, 3, 5, 7 [ C, E, G, B ]

Major 9th CMA9

1, 3, 5, 7, 9 [ C, E , G, B, D ]

Minor triad CMI

1, b3, 5 [ C, Eb , G ]

Minor 7th CMI7

1, b3, 5, b 7 [ C, Eb , G, Bb ]

Minor 9th CMI9

1, b3, 5, b7, 9 [ C, Eb , G , Bb , D ]

Dominant 7th C7

1, 3, 5, b7 [ C, E, G, Bb ]

Dominant 9th C9

1, 3, 5, b7, 9 [ C, E, G, Bb , D ]

Diminished triad C°

1, b3, b5 [ C, Eb , Gb ]

Minor 7 flat 5 CMI7b5

1, b3, b5, b7 [ C, Eb , Gb , Bb ]

Diminished 7th C°7

1, b3, b5, bb7 [ C, Eb , Gb , Bbb ]

If we now take this further, the extensions possible are the 11th and 13th chords. These chords will follow the same construction principals we have followed to get to this point. However, as we have seen with degrees III and VII not sustaining a 9th chord, we will also have to check carefully as to what is and what is not possible in constructing 11th and 13th chords. More on these in the next articles in this series.